It isn't about skin color, it's about culture: would a dark skinned Texan, from Dallas or Brownsville feel more comfortable and at home in predominantly white Wyoming, or in the Brighton Beach area of New York (almost entirely Russian descendants) or perhaps in the Muslim dominated areas of Michigan? Whenever there is no integration of immigrants into the community they adopt, life for the prior resident's changes beyond all previous recognition, yet any reasonable complaints are decried as xenophobic!
I've never understood that type of protectionist attitude. Unless you are native american you, like the vast majority of people in this country, either were an immigrant or are descended from one. So, is it, "I got mine, to hell with the rest of 'em?" You say it isn't about color and promptly site an example based on skin color. Of course it's about skin color! No on in the US is decrying Canadian immigration. Outside of the possible exception of an island, boarders are completely arbitrary. A large percentage of the countries in existence today didn't exist 50 years ago. As for culture: the US hasn't been around long enough to have a "culture" unless perhaps you want to count mass consumerism and materialism. The US is simply a combination of many cultures, and is the richer for it.